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Skeletal System

Skeletal System. Word Dissection. Roots You Will See Os bone Chon cartillage Practice: Osteocyte Chondrocyte. Skeletal System Functions:. Support: Structural frame Protection: some bones physically surround internal organs

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Skeletal System

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  1. Skeletal System

  2. Word Dissection Roots You Will See • Os bone • Chon cartillage Practice: Osteocyte Chondrocyte

  3. Skeletal System Functions: • Support: Structural frame • Protection: some bones physically surround internal organs • Aid in Movement: bones provide a place of attachment for muscles • Blood Cell formation: manufactured by red marrow (hematopoiesis) • Storage: storehouse for calcium and phosphate

  4. Bone Structure: Types of Bones • Long Bones- greater in length than width, absorb stress from body weight. EX/ Arm, leg Bones • Short Bones- about equal in length and width, forming a cube shape. EX/ wrist bones • Flat Bones- thin and flat. EX/ cranium bones • Irregular Bones- Do not fit into any other category. EX / vertebrae and bones of face

  5. Bone Classification Femur  • 4 types of bones: • Long Bones • Much longer than they are wide. • All bones of the limbs except for the patella (kneecap), • and the bones of the wrist and ankle. • Consists of a shaft plus 2 expanded ends. • Your finger bones are long bones even though they’re • very short – how can this be? • Short Bones • Roughly cube shaped. • Bones of the wrist and the ankle. Carpal Bones

  6. Bone Classification • Types of bones: • Flat Bones • Thin, flattened, and usually a bit curved. • Scapulae, sternum, (shoulder blades), ribs and most bones of the skull. • Irregular Bones • Have weird shapes that fit none of the 3 previous classes. • Vertebrae, hip bones, 2 skull bones ( sphenoid and the ethmoid bones). Sternum Sphenoid Bone

  7. Parts of a Long Bone- Exterior • Diaphysis – Long central shaft • Epiphyses- extreme ends of the bone, forms a joint or articulation • Articular cartilage- a thin layer of hyaline cartilage lies along the outer surface where joint occurs • Periosteum- a sheet of dense connective tissue that envelopes the bone, except where there is hyaline cartilage.

  8. Periosteum • Firmly attached to bones outer surface by protein fibers • Contains large supply of blood • Contains bone cell- osteoblast (active in bone growth • Functions: bone nourishment, attachment to ligaments and tendons, bone growth and repair

  9. Compact Bone Tightly packed Forms the walls of the diaphysis Spongy Bone Lattice network Occupies diaphysis Types of Bone Histological organization of compact bone (see Figure 19 below)

  10. All bones consist of a dense, solid outer layer known as compact bone and an inner layer of spongy bone – a honeycomb of flat, needle-like projections called trabeculae. • Bone is an extremely dynamic tissue!!!! Above: Note the relationship btwn the compact and spongy bone. Below:Close up of spongy bone.

  11. Note the gross differences between the spongy bone and the compact bone in the above photo. Do you see the trabeculae?

  12. Parts of Long Bone Cont. • Red Marrow- blood forming connective tissue • Medullary Cavity- large central chamber in the diaphysis (Compact bone) • Yellow marrow- located in the Medullary cavity, rich in fatty tissue for energy storage • Endosteum- interior lining of the Medullary cavity that extends into the spongy bone

  13. Location of hematopoietic Tissue (red marrow) In Infants – found on the medullary cavity and in spongy bone. In Adults – found in the spongy bone of flat bones and in the head of the femur and humerus

  14. Running perpendicular to the haversian canals are Volkmann’s canals. They connect the blood and nerve supply in the periosteum to those in the haversian canals and the medullary cavity.

  15. Osteons • Lying in between intact osteons are incomplete lamellae called interstitial lamellae. • There are also circumferential lamellae that extend around the circumference of the shaft. There are inner circumferential lamellae surrounding the endosteum and outer circumferential lamellae just inside the periosteum.

  16. Spider-shaped osteocytes occupy small cavities known as lacunae at the junctions of the lamellae. Hairlike canals called canaliculi connect the lacunae to each other and to the central canal. • Canaliculi allow the osteocytes to exchange nutrients, wastes, and chemical signals to each other via intercellular connections known as gap junctions.

  17. Bone Composition • Bone tissue, cartilage, dense connective tissue, blood forming tissue, blood vessels, and nerves • Primary component is bone tissue • Bone is a connective tissue. Strength Ca3(PO4)2 Calcium phosphate 2/3 by weight of bone Elasticity Collagen fibers Almost 1/3 of bone by weight Cells 2% of bone by weight

  18. Bone Tissue • Consists of hardened matrix, with embedded cells • Inorganic Materials- Hydroxyapatites, or mineral salts, calcium carbonate and calcium phosphate. 2/3 of bone, make it hard + inflexible • Organic Materials – mainly collagen, produced by bone cells, reinforces and strengthen matrix

  19. Three types of bone cells • Osteoblasts • Osteocytes • Osteoclasts

  20. Here, we see a cartoon showing all 3 cell types. • Note the size of the osteoclast (compare it to the osteoblast), and note the ruffled border. • Why is there a depression underneath the osteoclast? • What is the name of the third cell type shown here? • What do you think the tan material represents?

  21. Osteoblasts • Arise from embryonic cells • Within periosteum, in adults • Actively produce matrix, and get trapped in the chambers (lacunae)

  22. Osteocytes • Once osteoblasts become trapped in matrix they are call osteocytes – mature bone cells

  23. Osteoclasts • Wonder throughout the bone tissue • Secrete a substance that dissolves minerals salts crystals of matrix – resorb or break down bone matrix • http://www.youtube.com/watch?v=yENNqRJ2mu0 • http://courses.washington.edu/bonephys/physremod.html

  24. Yellow marrow Blood vessel

  25. Intramembranous bones: The bone is formed in and replaces a pre-existing membrane of embryonic connective tissue. A periosteum develops on the surfaces of the newly formed bone, and osteoblasts, which differentiate in it, continue the process of osteogenesis. Bones of the skull and jaw are examples.

  26. Endochondral bones:A cartilage model is formed initially; the cartilage is a temporary structure and is eventually destroyed except for the articular surface. Short and long bones are formed this way. Ossification: Synthesis of bone from cartilage

  27. Bone Classification • There are 206 named bones in the human body. • Each belongs to one of 2 groups: • Axial skeleton • Forms long axis of the body. • Includes the bones of the skull, vertebral column, and rib cage. • These bones are involved in protection, support, and carrying other body parts. • Appendicular skeleton • Bones of upper & lower limbs and the girdles (shoulder bones and hip bones) that attach to the axial skeleton. • Involved in locomotion and manipulation of the environment.

  28. Growth in length – cartilage continually grows and is replaced by bone as shown Remodeling – bone is resorbed and added by appositional growth as shown

  29. Hormonal Regulation of Bone Growth During Youth • During infancy and childhood, epiphyseal plate activity is stimulated by growth hormone (GH) • During puberty, by testosterone and estrogens • Initially promote adolescent growth spurts • Cause masculinization and feminization of specific parts of the skeleton • Later induce epiphyseal plate closure, ending longitudinal bone growth

  30. At puberty, growth in bone length is increased dramatically by the combined activities of growth hormone, thyroid hormone, and the sex hormones. • As a result osteoblasts begin producing bone faster than the rate of epiphyseal cartilage expansion. Thus the bone grows while the epiphyseal plate gets narrower and narrower and ultimately disappears. A remnant (epiphyseal line) is visible on X-rays (do you see them in the adjacent femur, tibia, and fibula?)

  31. Hormonal Mechanism • Rising blood Ca2+ levels trigger the thyroid to release calcitonin • Calcitonin stimulates calcium salt deposit in bone Figure 6.11

  32. Hormonal Mechanism • Falling blood Ca2+ levels signal the parathyroid glands to release PTH • PTH signals osteoclasts to degrade bone matrix and release Ca2+ into the blood Figure 6.11

  33. Response to Mechanical Stress • Wolff’s law – a bone grows or remodels in response to the forces or demands placed upon it Figure 6.12

  34. Response to Mechanical Stress • Observations supporting Wolff’s law include: • Long bones are thickest midway along the shaft (where bending stress is greatest) • Curved bones are thickest where they are most likely to buckle • Large, bony projections occur where heavy, active muscles attach Figure 6.12

  35. Fracture Types • Open (compound) bone ends penetrate the skin. • Closed (simple)  bone ends don’t penetrate the skin. • Comminuted bone fragments into 3 or more pieces. Common in the elderly (brittle bones). • Greenstickbone breaks incompletely. One side bent, one side broken. Common in children whose bone contains more collagen and are less mineralized. • Spiral ragged break caused by excessive twisting forces. Sports injury/Injury of abuse. • Impacted  one bone fragment is driven into the medullary space or spongy bone of another.

  36. Bone Fractures (Breaks) • Bone fractures are classified by: • The position of the bone ends after fracture • Completeness of the break • The orientation of the bone to the long axis • Whether or not the bones ends penetrate the skin http://video.about.com/osteoporosis/Fractures-2.htm

  37. Stages in the Healing of a Bone Fracture • Hematoma formation • Torn blood vessels hemorrhage • A mass of clotted blood (hematoma) forms at the fracture site • Site becomes swollen, painful, and inflamed Figure 6.13.1

  38. Stages in the Healing of a Bone Fracture • Fibrocartilaginous callus forms • Granulation tissue (soft callus) forms a few days after the fracture • Capillaries grow into the tissue and phagocytic cells begin cleaning debris Figure 6.13.2

  39. Stages in the Healing of a Bone Fracture • Bony callus formation • New bone trabeculae appear in the fibrocartilaginous callus • Fibrocartilaginous callus converts into a bony (hard) callus • Bone callus begins 3-4 weeks after injury, and continues until firm union is formed 2-3 months later Figure 6.13.3

  40. Stages in the Healing of a Bone Fracture • Bone remodeling • Excess material on the bone shaft exterior and in the medullary canal is removed • Compact bone is laid down to reconstruct shaft walls Figure 6.13.4

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